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Call Duration as an Indicator of Genetic Quality in Male Gray Tree Frogs
Allison M. Welch, Raymond D. Semlitsch, and H. Carl Gerhardt
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EVOLUTIONARY BIOLOGY: Females Pick Good Genes in Frogs, Flies
Elizabeth Pennisi
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Supplementary Material
Frog Don Juan. For gray tree frogs, it's the good genes, not just the long song, that win over the females.
C. GERHARDT
Download audio clips of frog calls to compare the long calls to the short. These frog calls were recorded by Dr. Alison Welch on May 12, 1995; each file contains two calls. The two frogs were calling within 2 m of one another and were both at 19 degrees C. The long calls are 24 and 26 pulses long (avg. 25 pulses) and 1.21 and 1.32 sec (avg. 1.27 sec). The short calls are 14 and 15 pulses (avg. 14.5 pulses) and 0.76 and 0.82 sec (avg. 0.79 sec). The long caller had a mass of 6.55 g and a snout-vent length (SVL) of 46 mm; the short caller had a mass of 7.45 g and an SVL of 47 mm.
Results of mixed-model analyses of variance and analyses of covariance. Analyses included the following main effects. "Call," a fixed effect, represented paternal call duration with two levels, long and short. In 1995, "family," a random effect, represented the nine maternal sibships, thereby encompassing effects of randomly-selected mothers and sets of long-and short-calling males. In 1996, "father," a fixed effect, represented the six sets of long- and short-calling males, while "mother," a random effect, represented the 11 randomly-selected mothers. Each ANOVA model was revised by sequentially excluding blocking terms and interactions that contributed little (
p>0.10) to the overall variance.
- Table 1 Results of mixed-model analyses of variance and analyses of covariance for the 1995 experiment at the high food level.
- Table 2 Results of mixed-model analyses of variance and analyses of covariance for the 1995 experiment at the low food level.
- Table 3 Results of mixed-model analyses of variance and analyses of covariance for the 1996 experiment at the high food level.
- Table 4 Results of mixed-model analyses of variance and analyses of covariance for the 1996 experiment at the low food level.
- Table 5 Performance of offspring of males exhibiting long versus short calls [mean +/-st. dev. (n)].
Table 1. Results of mixed-model analyses of variance and analyses of covariance for the 1995 experiment at the high food level.
| Source | df | MS | F | p |
|---|
| Larval growth |
| time | 1 | 0.3286 | 19.79 | 0.0001 |
| call | 1 | 0.0134 | 0.81 | 0.3706 |
| family | 8 | 0.0176 | 1.06 | 0.3947 |
| error | 169 | 0.0166 | | |
| Larval period |
| metamorphic mass | 1 | 2.78e-9 | 76.03 | 0.0001 |
| call | 1 | 3.46e-10 | 9.46 | 0.0025 |
| family | 8 | 4.96e-11 | 1.36 | 0.2193 |
| error | 156 | 3.66e-11 | | |
| Metamorphic mass |
| larval period | 1 | 2.42e-2 | 31.04 | 0.0001 |
| time | 1 | 7.15e-3 | 3.47 | 0.0913 |
| block (time) | 13 | 1.26e-3 | 1.62 | 0.0892 |
| call | 1 | 2.35e-4 | 0.14 | 0.7161 |
| family* | 8 | 1.47e-3 | 0.42 | 0.8865 |
| time x family | 8 | 2.63e-3 | 3.39 | 0.0015 |
| call x family | 8 | 1.73e-3 | 2.23 | 0.0294 |
| error | 126 | 7.78e-4 | | |
| Larval survival |
| time | 1 | 1.2261 | 5.29 | 0.0504 |
| call | 1 | 0.1293 | 4.72 | 0.0442 |
| family* | 8 | 0.1586 | 0.68 | 0.6976 |
| time x family | 8 | 0.2316 | 8.46 | 0.0001 |
| error | 17 | 0.0274 | | |
* The two-way interaction term was used in constructing the F-statistic instead of the overall error term, providing a more conservative test.
Table 2. Results of mixed-model analyses of variance and analyses of covariance for the 1995 experiment at the low food level.
| Source | df | MS | F | p |
|---|
| Larval growth |
| time | 1 | 6.84e-3 | 39.83 | 0.0001 |
| block (time) | 10 | 4.38e-4 | 2.55 | 0.0182 |
| call | 1 | 2.03e-3 | 3.83 | 0.0821* |
| family** | 8 | 2.92e-4 | 0.47 | 0.8497 |
| call x family | 8 | 6.10e-4 | 3.55 | 0.0037 |
| error | 38 | 1.72e-4 | |
|
| Larval period |
| metamorphic mass | 1 | 5.50e-11 | 11.24 | 0.0019 |
| time | 1 | 1.72e-11 | 3.53 | 0.0686 |
| call | 1 | 7.58e-12 | 1.55 | 0.2211 |
| family | 7 | 6.88e-12 | 1.41 | 0.2325 |
| error | 36 | 4.89e-12 | |
|
| Metamorphic mass |
| larval period | 1 | 2.57e-3 | 13.22 | 0.0009 |
| time | 1 | 9.67e-4 | 4.98 | 0.0319 |
| call | 1 | 1.44e-3 | 7.39 | 0.0100 |
| family | 7 | 4.60e-4 | 2.37 | 0.0424 |
| error | 36 | 1.94e-4 | |
|
| Larval survival |
| call | 1 | 0.1961 | 2.72 | 0.1111 |
| family | 8 | 0.1164 | 1.61 | 0.1690 |
| error | 26 | 0.0721 | | |
* In a separate analysis of variance with the call x family interaction excluded, the main effect of call duration was highly significant (F=7.546,
p=0.0085), indicating that the interaction is largely due to a difference between offspring of long- and short-callers. Furthermore, a t-test on least squares means revealed a highly significant difference (t
65=3.44,
p=0.0014) between offspring of long- and short-calling males.
** The two-way interaction term was used in constructing the F-statistic instead of the overall error term, providing a more conservative test.
Table 3. Results of mixed-model analyses of variance and analyses of covariance for the 1996 experiment at the high food level.
| Source | df | MS | F | p |
|---|
| Larval growth |
| call* | 1 | 0.2181 | 11.26 | 0.0028 |
| father* | 2 | 0.0481 | 2.28 | 0.1302 |
| mother* | 7 | 0.0217 | 1.06 | 0.4253 |
| call x father x mother | 18 | 0.0212 | 1.89 | 0.0208 |
| error | 139 | 0.0112 | | |
| Larval period |
| metamorphic mass | 1 | 3.39e-7 | 15.83 | 0.0001 |
| call | 1 | 2.12e-7 | 9.89 | 0.0021 |
| father | 2 | 1.16e-8 | 0.54 | 0.5840 |
| mother | 7 | 3.15e-8 | 1.47 | 0.1834 |
| error | 133 | 2.14e-8 | | |
| Metamorphic mass |
| larval period | 1 | 1.78e-2 | 9.76 | 0.0022 |
| block | 5 | 4.35e-3 | 2.39 | 0.0415 |
| call | 1 | 6.00e-4 | 0.33 | 0.5668 |
| father | 2 | 4.73e-3 | 2.60 | 0.0783 |
| mother | 7 | 9.45e-3 | 5.19 | 0.0001 |
| error | 128 | 1.82e-3 | | |
| Juvenile growth |
| metamorphic mass | 1 | 35835.6 | 30.79 | 0.0001 |
| call | 1 | 3.03658 | 0.003 | 0.9594 |
| father | 2 | 1144.22 | 0.98 | 0.3789 |
| mother** | 7 | 2007.30 | 1.18 | 0.3228 |
| block x mother | 54 | 1786.49 | 1.53 | 0.0434 |
| error | 74 | 1163.69 | | |
| Larval survival |
|---|
| call | 1 | 0.0540 | 0.39 | 0.5470 |
| father | 2 | 0.0079 | 0.17 | 0.8462 |
| mother** | 6 | 0.0756 | 0.51 | 0.7858 |
| call x mother | 9 | 0.1518 | 3.23 | 0.0065 |
| error | 33 | 0.0470 | | |
* The three-way interaction term was used in constructing the F-statistic instead of the overall error term, providing a more conservative test.
** The two-way interaction term was used in constructing the F-statistic instead of the overall error term, providing a more conservative test.
Table 4. Results of mixed-model analyses of variance and analyses of covariance for the 1996 experiment at the low food level.
| Source | df | MS | F | p |
|---|
| Larval growth |
| call | 1 | 3.01e-3 | 5.98 | 0.0159 |
| father | 2 | 1.59e-4 | 0.31 | 0.7305 |
| mother | 7 | 6.18e-4 | 1.23 | 0.2933 |
| block x mother | 29 | 7.84e-4 | 1.56 | 0.0503 |
| error | 128 | 5.04e-4 | | |
| Larval period |
| metamorphic mass | 1 | 0.0807 | 6.92 | 0.0122 |
| call* | 1 | 0.0449 | 1.78 | 0.1995 |
| father* | 2 | 0.0259 | 1.05 | 0.3691 |
| mother* | 7 | 0.0307 | 1.28 | 0.3104 |
| call x father x mother | 15 | 0.0275 | 2.36 | 0.0163 |
| error | 38 | 0.0117 | | |
| Metamorphic mass |
| larval period | 1 | 2.80e-3 | 3.69 | 0.0601 |
| call | 1 | 1.83e-5 | 0.02 | 0.8773 |
| father | 2 | 2.53e-3 | 3.33 | 0.0433 |
| mother | 7 | 1.81e-3 | 2.38 | 0.0416 |
| error | 53 | 7.60e-4 | | |
| Juvenile growth |
| metamorphic mass | 1 | 1.71e-3 | 1.22 | 0.2775 |
| call | 1 | 1.49e-2 | 10.69 | 0.0028 |
| father | 1 | 6.87e-4 | 0.49 | 0.4890 |
| mother | 3 | 2.49e-3 | 1.78 | 0.1727 |
| error | 29 | 1.40e-3 | | |
| Larval survival |
| call | 1 | 0.0545 | 0.34 | 0.5617 |
| father | 2 | 0.6337 | 3.97 | 0.0259 |
| mother | 7 | 0.2298 | 1.44 | 0.2136 |
| error | 44 | 0.1595 | | |
* The three-way interaction term was used in constructing the F-statistic instead of the overall error term, providing a more conservative test.
Table 5. Performance of offspring of males exhibiting long versus short calls [mean ± st. dev. (n)].
| Parameter | Call duration | 1995 | 1996 |
|---|
| High food | Low food | High food | Low food |
|---|
| Larval growth (g) |
Long | 0.6335±0.1332 (88) | 0.3423±0.0669 (28) | 0.5768±0.1209 (81) | 0.2274±0.0574 (76) |
| Short | 0.6538±0.1087 (92) | 0.3078±0.0559 (39) | 0.5142±0.1058 (90) | 0.2078±0.0595 (95) |
| Larval period (d) |
Long | 34.48±4.02 (85) | 53.40±7.76 (20) | 42.51±7.98 (69) | 71.91±10.55 (32) |
| Short | 36.45±5.13 (82) | 52.78±6.84 (27) | 46.29±8.29 (79) | 74.44±11.90 (36) |
| Metamorphic mass (g) |
Long | 0.3559±0.0491 (85) | 0.2722±0.0379 (20) | 0.3178±0.0575 (69) | 0.2466±0.0310 (32) |
| Short | 0.3616±0.0553 (82) | 0.2474±0.0288 (27) | 0.3212±0.0606 (79) | 0.2536±0.0403 (36) |
| Larval survival |
Long | 0.702±0.115 (9) | 0.156±0.137 (9) | 0.922±0.119 (14) | 0.544±0.229 (15) |
| Short | 0.637±0.101 (9) | 0.237±0.130 (9) | 0.905±0.156 (14) | 0.524±0.214 (15) |
| Post-metamorphic growth (g) |
Long | - | - | 0.0694±0.0476 (67) | 0.0529±0.0386 (17) |
| Short | - | - | 0.0678±0.0415 (76) | 0.0174±0.0415 (22) |
